KOI 172.02 is about the same size as Earth, and orbits a star similar to our own at about the same distance.

Its radius is just 1.5 times that of Earth and it orbits a star similar to the Sun, within the "habitable zone" where liquid water could exist.

KOI 172.02's sun is slightly cooler than our own, and the planet is located slightly closer to its surface. It orbits at about 70 million miles, compared to 93 million miles between the Earth and the Sun.

It has an orbit of 242 days, compared to our 365.

The planet is the first Earth-like planet found orbiting a Sun-like star in the habitable zone - making it a so-called "big deal" according to investigators at Nasa.